EP0073591A1 - Zahnstangenritzelanordnung - Google Patents

Zahnstangenritzelanordnung Download PDF

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Publication number
EP0073591A1
EP0073591A1 EP82304286A EP82304286A EP0073591A1 EP 0073591 A1 EP0073591 A1 EP 0073591A1 EP 82304286 A EP82304286 A EP 82304286A EP 82304286 A EP82304286 A EP 82304286A EP 0073591 A1 EP0073591 A1 EP 0073591A1
Authority
EP
European Patent Office
Prior art keywords
neck portion
transmission element
rack
rib
bellows
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82304286A
Other languages
English (en)
French (fr)
Inventor
Christopher Philip James Boucher
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
TRW Steering Systems Ltd
Original Assignee
TRW Steering Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by TRW Steering Systems Ltd filed Critical TRW Steering Systems Ltd
Publication of EP0073591A1 publication Critical patent/EP0073591A1/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D3/00—Steering gears
    • B62D3/02—Steering gears mechanical
    • B62D3/12—Steering gears mechanical of rack-and-pinion type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J3/00—Diaphragms; Bellows; Bellows pistons
    • F16J3/04—Bellows
    • F16J3/041—Non-metallic bellows

Definitions

  • the present invention relates to rack and pinion assemblies and is particularly concerned with a rack and pinion assembly of the type (hereinafter referred to as "the type specified") which comprises a pinion rotatably mounted in a pinion housing, a rack bar linearly movable in a longitudinal direction through the pinion housing and within an elongate rack bar housing associated with the pinion housing, a toothed rack on the rack bar which operatively engages with the pinion so that rotation of the pinion effects movement of the rack bar longitudinally through the housings, a transmission element coupled to one end of the rack bar and extending generally longitudinally therefrom outwardly of the rack bar housing for longitudinal displacement with the rack bar, and a tubular bellows which extends in fluid sealing manner between the rack bar housing and the transmission element and which expands and contracts with longitudinal displacement of the rack bar through the housings and with concurrent longitudinal displacement of the transmission element relative to the rack bar housing.
  • Rack and pinion assemblies of the type specified are particularly, but not essentially, used with steering assemblies for vehicles and in this case a respective transmission element, for example in the form of a tie rod, may be coupled to each end of the rack bar, each such transmission element having a respective bellows associated therewith and being adapted to be coupled to a respective steerable road wheel.
  • a respective transmission element for example in the form of a tie rod
  • Rack and pinion assemblies of the type specified are well known and have been used in steering assemblies for vehicles for several years.
  • One of the problems associated with rack and pinion assemblies is to ensure the fluid seal at the end of the rack bar housing from which the transmission element extends outwardly.
  • the tubular bellows of natural or synthetic rubber or, for example, polyurethane has traditionally performed this function, but the difficulty with the bellows is adequately sealing it at its connection with the transmission element, which is usually of circular cross-section and of relatively small diameter (i.e. 12 mm).
  • the connecting portion of the bellows being formed of rubber or polyurethane of relatively low resilience
  • one proposal for providing the fluid sealing connection between the bellows and the transmission element has been to form the cross-section of the connecting neck of the bellows substantially smaller than that of the transmission element so that the neck must be stretched and slid over the element.
  • the relatively low resilience of the material of the neck has raised the possibility that with continual flexing of the bellows, the fluid may be able to escape between the neck and the transmission element.
  • the securing means have taken the form of adhesive to bond the neck and transmission element together, or of various types of clip which tighten the grip of the neck on the transmission element.
  • the tracking of the wheels must be set initially and occasionally re-adjusted with the steering assembly in the vehicle. Adjusting the wheel tracking requires adjustment of the distance between the distal ends of the transmission elements to which the wheels are respectively coupled by, for example, ball joints. Generally each transmission element is connected to the associated coupling by a screw threaded engagement and the transmission elements are rotatable to adjust said distance between-the distal.ends and thereby the tracking. If the bellows is clipped to the transmission element as aforesaid it must be released before the tracking is set or the bellows will be screwed up with the transmission element so that it cannot operate properly and may break easily. After setting the tracking the clips must be re-tightened which requires an additional labour step, or if the re-tightening is omitted, the fluid seal is lost.
  • a rack and pinion assembly of the type specified in which the fluid sealing engagement between the transmission element and the bellows is at a neck portion of the bellows which is of substantially the same internal cross-section as.the cross-section of the transmission element, and wherein a peripheral recess is provided in one of the transmission element and the internal wall of the neck portion and a co-operating peripheral rib is provided on the other of the transmission element and internal wall of the neck portion, and further wherein the neck portion is formed of a resilient material which permits sliding movement of the neck portion over the transmission element and snap engagement of the peripheral rib and recess with such force and retaining effect that, in the absence of other retaining means, the rib and recess maintain said fluid sealing engagement throughout the intended expansions and contractions of the bellows in use.
  • a steering gear assembly comprising a rack and pinion assembly substantially as described in the preceding paragraph.
  • the Young's Modulus should be relatively high, and substantially higher than that of the rubbers and polyurethanes used conventionally in the neck portions of bellows in rack and pinion assemblies, so that the internal cross-sectional area of the neck portion varies little during assembly.
  • a preferred material for the neck portion of the bellows, and which may be used for the bellows as a whole, is a polyester polyether grade of thermoplastics elastomer, for example that sold under the Trade Mark HYTREL by DuPont Inc.,
  • the peripheral recess is formed in the transmission element and the peripheral rib is formed in the internal wall of the neck portion, for example during moulding of the bellows.
  • the thickness of the material of the neck portion is substantially the same at the location of the rib as elsewhere so that a corresponding recess is formed in the external wall of the neck portion.
  • the peripheral rib may be approximately 1 mm deep.
  • the peripheral rib is preferably rounded, i.e. of arcuate cross-section, and where the rib is formed on the neck portion., the end of the transmission element on to which the neck portion is introduced during assembly may be rounded or tapered to further facilitate assembly.
  • the peripheral recess with which the peripheral rib snap-engages may be substantially straight-sided with the sides extending at least perpendicularly to the surface of the transmission element over which the neck portion is slid to provide the snap engagement but is preferably also of arcuate cross-section and of substantially the same radius as the aforementioned arcuate cross-section of the rib.
  • the combination may be such as to prevent removal of the bellows from the transmission element without cutting the bellows open, or otherwise straining the neck portion beyond its elastic limit.
  • the rack bar assembly in accordance with the present invention and shown in the drawings comprises an elongate rack bar housing 1 through which is longitudinally movable a rack bar (not shown).
  • the rack bar is moved longitudinally in known manner by means of a rotatively mounted pinion (not shown), which in the case of a steering assembly may be connected to a vehicle steering wheel (not shown).
  • the pinion is mounted in a pinion housing (not shown) associated with the rack bar housing 1.
  • the rack bar housing 1 is tubular and has an open end 2 and from the open end 2 projects a transmission element 3, which in the case of a steering assembly may be in the form of a tie rod.
  • the transmission element 3 is coupled at its end within the housing 1 to one end of the rack bar, usually by means of a universally-movable joint.
  • the other end of the transmission element is coupled, in the case-of a steering assembly, to a steerable road wheel and generally in known manner a further steerable road wheel will be coupled through a further transmission element to the other end of the rack bar.
  • the transmission element 3 is shown as extending with the rack bar housing 1, it will be appreciated that the rack bar may extend into the bellows.
  • Lubrication fluid is provided within the rack bar housing 1 and a tubular sealing bellows 4 is provided between the open end 2 of the rack bar housing 1 and the transmission element 3 to provide a fluid seal.
  • FIGURE 1 the tubular bellows 4 and rack bar housing 1 are shown in section on one side of the axis X-X only, but it will be appreciated that the view on the other side of the axis would be essentially a mirror image of the view shown..
  • tubular bellows 4 At its end connected to the open end 2 of the rack bar housing 1 the tubular bellows 4 is provided with an annular flat 5 which overlaps in close-fitting manner a corresponding portion of the end 2.
  • annular clamp or clip 6 In order to retain the bellows on the end 2, a suitable and known annular clamp or clip 6 is used which is shown in schematic form only.
  • the bellows 4 has a plurality of annular corrugations 7 and is formed, for example, by injection or blow moulding, from a thermoplastics elastomeric material of relatively high resilience such as a polyester polyether, an example of which is marketed under the Trade Mark HYTREL by DuPont Inc..
  • a thermoplastics elastomeric material of relatively high resilience such as a polyester polyether, an example of which is marketed under the Trade Mark HYTREL by DuPont Inc.
  • the thickness of the material of the corrugations 7 reduces with increasing radius and in conjunction with an ability of the material to flex, the corrugations permit the contraction and expansion of the bellows during longitudinal movement of the transmission element 3 in and out of the rack bar housing 1.
  • the material however has a relatively high Young's Modulus with the result that it is difficult to stretch.
  • the bellows has a frusto-conical part 9 which extends from the end of the corrugations to a neck portion 10 which has an internal diameter substantially the same as that of the transmission element 3.
  • the thickness of the material of the bellows increases gradually with decreasing diameter of the frusto-conical part 9 and the neck portion 10 is relatively inflexible.
  • the stiffness of the neck portion 10 and frusto-conical part 9 may be increased by tapered ribs such as that shown at 11 in dotted lines in FIGURE 1-
  • Formed substantially centrally, in the axial direction, of the neck portion 10 is an annular rib 12 which projects radially inwardly of the inner surface of the neck portion.
  • the rib 12 is moulded into the neck portion and the thickness of the material of the neck portion 10 is maintained through the rib 12 so that a corresponding groove 13 is defined on the radially outer surface of the neck portion.
  • the rib 12 co-operates with an annular recess 14 formed in the transmission element.
  • the neck portion 10 is forced on to the transmission element 3 and slid therealong until the rib 12 snap-engages into the recess 14.
  • the neck portion 10 of the bellows is of substantially the same diameter as the transmission element with the rib 12 projecting inwardly of said diameter. Accordingly, the rib 12 must be forced over the end of the transmission element and this is permitted by the resilient material of the neck portion 10 because the degree of flexibility in the material allows the annular rib 12 and corresponding groove 13 to at least partially flatten out with the rest of the neck portion.
  • the resilience of the material causes snap engagement with such force and retaining effect that, in the absence of additional clips, adhesive and such like, the rib 12 maintains fluid sealing engagement with the recess 14 throughout the intended length variations required of the bellows in use.
  • the rib 12 has a rounded shape, i.e. it is of arcuate cross-section, and this facilitates the sliding engagement of the rib with the end of the transmission element.
  • end of the transmission element may be tapered (not shown) whereby the increase in diameter of the rib 12 during assembly of the neck portion 10 on to the transmission element 3 is gradual.
  • the annular recess 14 is likely to be located adjacent such end of the transmission element.
  • the recess 14 is arcuate ' in cross-section and of substantially the same radius as the rib 12, and this reduces further any possibility of the rib 12 being withdrawn from the recess 14.
  • the bellows 4 in a rack and pinion assembly in accordance with the present invention is prevented from being removed from the transmission element 3 by the rib and recess and that such removal must be by cutting.
  • the combination of material of high resilience, and the shape and relative sizes of the neck portion 10 and transmission element 3 and the rib 12 and recess 14 therein may be used to provide this feature.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Diaphragms And Bellows (AREA)
  • Sealing Devices (AREA)
EP82304286A 1981-08-13 1982-08-13 Zahnstangenritzelanordnung Withdrawn EP0073591A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8124832 1981-08-13
GB8124832 1981-08-13

Publications (1)

Publication Number Publication Date
EP0073591A1 true EP0073591A1 (de) 1983-03-09

Family

ID=10523935

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82304286A Withdrawn EP0073591A1 (de) 1981-08-13 1982-08-13 Zahnstangenritzelanordnung

Country Status (1)

Country Link
EP (1) EP0073591A1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4936811A (en) * 1989-03-20 1990-06-26 Wynn's-Precision, Inc. Boot assembly for constant velocity joint
EP0669478A1 (de) * 1994-02-24 1995-08-30 Draftex Industries Limited Schutzbalg
FR2862737A1 (fr) * 2003-11-26 2005-05-27 Linde Ag Dispositif pour realiser l'etancheite du passage a travers la paroi d'un boitier a isolation thermique

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1933391U (de) * 1965-12-03 1966-02-24 Ehrenreich & Cie A Balgdichtung fuer allseitig bewegliche gelenke, insbesondere kugelgelenke.
GB1081265A (en) * 1966-01-31 1967-08-31 Ford Motor Co Rack and pinion steering gear for a motor vehicle
DE2147454A1 (de) * 1971-09-23 1973-03-29 Continental Gummi Werke Ag Rollmanschette, insbesondere fuer keilwellen
DE2734516A1 (de) * 1977-07-30 1979-02-15 Audi Nsu Auto Union Ag Zahnstangenlenkung fuer kraftfahrzeuge

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1933391U (de) * 1965-12-03 1966-02-24 Ehrenreich & Cie A Balgdichtung fuer allseitig bewegliche gelenke, insbesondere kugelgelenke.
GB1081265A (en) * 1966-01-31 1967-08-31 Ford Motor Co Rack and pinion steering gear for a motor vehicle
DE2147454A1 (de) * 1971-09-23 1973-03-29 Continental Gummi Werke Ag Rollmanschette, insbesondere fuer keilwellen
DE2734516A1 (de) * 1977-07-30 1979-02-15 Audi Nsu Auto Union Ag Zahnstangenlenkung fuer kraftfahrzeuge

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4936811A (en) * 1989-03-20 1990-06-26 Wynn's-Precision, Inc. Boot assembly for constant velocity joint
EP0669478A1 (de) * 1994-02-24 1995-08-30 Draftex Industries Limited Schutzbalg
FR2862737A1 (fr) * 2003-11-26 2005-05-27 Linde Ag Dispositif pour realiser l'etancheite du passage a travers la paroi d'un boitier a isolation thermique

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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AK Designated contracting states

Designated state(s): DE FR GB IT

17P Request for examination filed

Effective date: 19830209

STAA Information on the status of an ep patent application or granted ep patent

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18D Application deemed to be withdrawn

Effective date: 19841017

RIN1 Information on inventor provided before grant (corrected)

Inventor name: BOUCHER, CHRISTOPHER PHILIP JAMES